/*
* 2002-10-18 written by Jim Houston jim.houston@ccur.com
* Copyright (C) 2002 by Concurrent Computer Corporation
* Distributed under the GNU GPL license version 2.
*
* Modified by George Anzinger to reuse immediately and to use
* find bit instructions. Also removed _irq on spinlocks.
*
* Modified by Nadia Derbey to make it RCU safe.
*
* Small id to pointer translation service.
*
* It uses a radix tree like structure as a sparse array indexed
* by the id to obtain the pointer. The bitmap makes allocating
* a new id quick.
*
* You call it to allocate an id (an int) an associate with that id a
* pointer or what ever, we treat it as a (void *). You can pass this
* id to a user for him to pass back at a later time. You then pass
* that id to this code and it returns your pointer.
* You can release ids at any time. When all ids are released, most of
* the memory is returned (we keep IDR_FREE_MAX) in a local pool so we
* don't need to go to the memory "store" during an id allocate, just
* so you don't need to be too concerned about locking and conflicts
* with the slab allocator.
*/
#ifndef TEST // to test in user space...
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/module.h>
#endif
#include <linux/err.h>
#include <linux/string.h>
#include <linux/idr.h>
#include <linux/spinlock.h>
static struct kmem_cache *idr_layer_cache;
static DEFINE_SPINLOCK(simple_ida_lock);
static struct idr_layer *get_from_free_list(struct idr *idp)
{
struct idr_layer *p;
unsigned long flags;
spin_lock_irqsave(&idp->lock, flags);
if ((p = idp->id_free)) {
idp->id_free = p->ary[0];
idp->id_free_cnt--;
p->ary[0] = NULL;
}
spin_unlock_irqrestore(&idp->lock, flags);
return(p);
}
static void idr_layer_rcu_free(struct rcu_head *head)
{
struct idr_layer *layer;
layer = container_of(head, struct idr_layer, rcu_head);
kmem_cache_free(idr_layer_cache, layer);
}
static inline void free_layer(struct idr_layer *p)
{
call_rcu(&p->rcu_head, idr_layer_rcu_free);
}
/* only called when idp->lock is held */
static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
{
p->ary[0] = idp->id_free;
idp->id_free = p;
idp->id_free_cnt++;
}
static void move_to_free_list(struct idr *idp, struct idr_layer *p)
{
unsigned long flags;
/*
* Depends on the return element being zeroed.
*/
spin_lock_irqsave(&idp->lock, flags);
__move_to_free_list(idp, p);
spin_unlock_irqrestore(&idp->lock, flags);
}
static void idr_mark_full(struct idr_layer **pa, int id)
{
struct idr_layer *p = pa[0];
int l = 0;
__set_bit(id & IDR_MASK, &p->bitmap);
/*
* If this layer is full mark the bit in the layer above to
* show that this part of the radix tree is full. This may
* complete the layer above and require walking up the radix
* tree.
*/
while (p->bitmap == IDR_FULL) {
if (!(p = pa[++l]))
break;
id = id >> IDR_BITS;
__set_bit((id & IDR_MASK), &p->bitmap);
}
}
/**
* idr_pre_get - reserve resources for idr allocation
* @idp: idr handle
* @gfp_mask: memory allocation flags
*
* This function should be called prior to calling the idr_get_new* functions.
* It preallocates enough memory to satisfy the worst possible allocation. The
* caller should pass in GFP_KERNEL if possible. This of course requires that
* no spinning locks be held.
*
* If the system is REALLY out of memory this function returns %0,
* otherwise %1.
*/
int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
{
while (idp->id_free_cnt < IDR_FREE_MAX) {
struct idr_layer *new;
new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
if (new == NULL)
return (0);
move_to_free_list(idp, new);
}
return 1;
}
EXPORT_SYMBOL(idr_pre_get);
static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
{
int n, m, sh;
struct idr_layer *p, *new;
int l, id, oid;
unsigned long bm;
id = *starting_id;
restart:
p = idp->top;
l = idp->layers;
pa[l--] = NULL;
while (1) {
/*
* We run around this while until we reach the leaf node...
*/
n = (id >> (IDR_BITS*l)) & IDR_MASK;
bm = ~p->bitmap;
m = find_next_bit(&bm, IDR_SIZE, n);
if (m == IDR_SIZE) {
/* no space available go back to previous layer. */
l++;
oid = id;
id = (id | ((